An index print is a single print comprised of a matrix of small images corresponding to individual negative frames on a strip of photographic film. This type of print is desirable for the customer in that positive image reproductions are provided for convenient reference by the customer to indicate the content of the film without having to view the film directly. This is of particular benefit for negative film since the scene content of negative images is difficult to visualize, particularly by an untrained viewer.
At the present time, index prints are not generally produced by photofinishing laboratories although technology for doing so is known. The reason for this is believed to reside in the difficulty of doing so and the cost associated with extra equipment needed to produce the prints. In general, there are two basic techniques known for the production of index prints. One is to optically print the negative film frames onto photographic paper by contact printing or some other type of printing device. The disadvantage of this technique is that it requires separate equipment and extra handling of the film as will as additional time added to the overall print order processing.
Another technique involves scanning the negative frames with an electronic film scanner with equipment over and above that used in the normal photofinishing process and producing the index prints with a hardcopy output device, such as a cathode ray tube (CRT) printer, laser printer, thermal printer or the like. Examples of this technique are found in U.S. Pat. Nos. 4,903,068 and 4,933,773. In the '068 patent a CRT scanning light source is used to expose the film frames onto the photopaper to produce the customer's print order. Simultaneously, a portion of the scanned image light is deflected to auxiliary digital image processing and memory circuits. When a predetermined number of frames have been printed, the corresponding stored digital image are recalled from memory and used to drive the CRT exposure scanner to produce an index print of the stored images as a matrix of reduced-size images on the next available space on the photopaper. The '773 patent is similar except that a non-scanning exposure light source is used for the principal print exposures. A portion of the image exposure light is deflected to a video camera and subsequent processing circuits wherein the image is scanned and digitized for storage in memory. After the appropriate number of frames are printed, the corresponding stored image are recalled from memory and an index print exposure made by means of an auxiliary scanning CRT light source. Both of these examples require significant additional capital investment for the added equipment required.